Line widths and velocities for Balmer lines of the Lupus sample. Left panels: FWHM of Hβ versus FWHM of Hα (top); FWHM of H9 versus FWHM of Hβ (bottom). Central panels: red/blue wings extension in Hβ (top) and H9 (bottom). Right panels: FWZI versus FWHM for Hβ (top) and H9 (bottom); dashed lines mark the expected correlation between the FWHM and FWZI (measured at 1/30, 1/50, and 1/100 of the peak) in a Gaussian profile. The different symbols indicate the line profile typology (see Sect. 3.1 and Table 1: narrow symmetric (circles), wide symmetric (squares), and asymmetric or multi-peaked (crosses). Sources where the Hα or Hβ present a particularly deep central absorption, which may introduce a strong bias in the line FWHM measurement (see text), are marked with a red circle.